Pixelorama/src/Shaders/Effects/Invert.gdshader

shader_type canvas_item;
render_mode unshaded;

uniform bool red = true;
uniform bool blue = true;
uniform bool green = true;
uniform bool alpha = false;
uniform sampler2D selection : filter_nearest;


void fragment() {
	// Get color from the sprite texture at the current pixel we are rendering
	vec4 original_color = texture(TEXTURE, UV);
	vec4 selection_color = texture(selection, UV);
	vec4 col = original_color;
    if (red)
        col.r = 1.0 - col.r;
    if (green)
        col.g = 1.0 - col.g;
    if (blue)
        col.b = 1.0 - col.b;
    if (alpha)
        col.a = 1.0 - col.a;

	vec4 output = mix(original_color.rgba, col, selection_color.a);
	COLOR = output;
}